The universe is enormous, it has to be. It's endless. Given its enormity it stands to reason that somewhere out there may be another form of life. We down here do not expect to find life like humans, however if there is life on another planet, we know for certain that it would have to meet these conditions:

- Solvent - Here on Earth, we have a universal solvent: water. There must exist one such substance that can dissolve biochemicals. Other potential solvents could be ammonia, methane, hydrogen sulfide or hydrogen fluoride.

- Temperature - Alien life may require temperatures at which its solvent can remain liquid

- Pressure - Alien life may require environmental pressures (and temperatures) that allow solvents to exist in three states of matter (solid, liquid, gas).

- Energy source - Living things require energy to remain organized. This energy may come from a star or from chemical or geothermal energy (as in hydrothermal vents and hot springs). On any alien world, there would have to be some source of energy to sustain life.

- Complex molecules - Living things on Earth are organized and made of complex, carbon-based molecules that carry out biochemical functions. Carbon is a versatile atom that can form bonds with up to four other atoms, in many shapes, to make molecules. Although not as versatile as carbon, silicon can also form up to four bonds with other atoms and has been proposed as a basis for molecules of alien life (silicon-carbon hybrid molecules have also been proposed). It is likely that alien life forms would have some type of complex molecule to carry out similar functions.

- Informational molecule - In Earth organisms, deoxyribonucleic acid (DNA) is a complex molecule that carries genetic information and directs the formation of other molecules in order for life to reproduce and function. Because a characteristic of life is that it reproduces, it seems likely that alien life forms would also have some type of informational molecule. There is a small bottle containing a red fluid on a shelf in Sheffield University's microbiology laboratory. The liquid looks cloudy and uninteresting. Yet, if one group of scientists is correct, the phial contains the first samples of extraterrestrial life isolated by researchers.